A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

no longer supported. This tag is for the Official Stack Exchange application only. The app is available in the App Store, for iOS 8+ on iPhones and iPads. When posting bug report…
1409 questions
the governing meta site for all Stack Exchange sites together. Use this tag to ask questions about this very site, a.k.a. MSE. In some sense, the [meta] tag is Meta-Meta Stack Exchange.
For questions about the functionalities, queries, databases and datamodel of The Stack Exchange Data Explorer (SEDE). SEDE allows you to create and run queries against copies of the databases of popul…
Questions about the various user interface and email elements used to notify users of events on the site.
1309 questions
General questions about questions that have been closed because they are off-topic or otherwise do not meet the criteria defined in the FAQ.
1308 questions
For questions or issues surrounding login to Stack Exchange sites.
Use along with [meta] to ask about specific questions here on Meta Stack Exchange. Questions about questions on other network sites are off-topic here and should be posted on the site's meta instead.
1286 questions
the process of migrating off-topic questions from a Stack Exchange site to another.
1252 questions
the answer the question owner thought best met their needs. This tag is for discussing issues related to accepted answers, not indicating that a question has an accepted answer.
1155 questions
for questions specifically about the process of asking questions on a Stack Exchange site.
1129 questions
Refers to user accounts either generically, or across the network.
For questions about the mobile versions of Stack Exchange sites. For questions about the mobile apps, use the [android-app] and the [ios-app] tags as needed. Since the new responsive design will event…
refers to all questions deleted from Stack Exchange sites. You can also use this tag along with [specific-question] and [meta] to ask why a specific question on Meta Stack Exchange was delete…
1017 questions
those users who may be new to the Stack Exchange Q&A format, and generally have a low reputation score, which starts from 1 at the time of registration.
870 questions
abilities you earn with increased reputation to do and see more on the site. Use this tag for questions about privilege levels and privilege notifications.
827 questions
for questions about tag synonyms (how they work, who can create them, etc). To request a tag synonym, ask on the per-site meta with the tag [synonym-request].
801 questions
for instructions and guidance on closing or migrating questions, and the reasons for those closures.
790 questions
the tag to use for any questions related to deleted answers specifically.
778 questions
for requests to replace one tag with another existing tag. It also applies to requests that one tag should be merged into another, or simply abandoned.
759 questions
Indicates that the site developers were not able to replicate the behavior reported.
755 questions
the norms and standards of accepted behavior and politeness in our community. The golden rule is "Think before you post."
750 questions
The black bar across the top of every Stack Exchange site.
709 questions
for questions dealing with moderator actions, pages, abilities or decisions.
683 questions
For questions about the images used on Stack Exchange sites or about using images in your own posts.
668 questions
For questions about making code appear correctly in questions, answers and comments.
663 questions
for questions about suspected user spam, the spam flag or combating spam as a community.
662 questions
Questions about diamond (♦) moderators, their powers, and actions they have taken.
an editable page that briefly summarizes the topic of the tag and that may provide links to existing questions that are often useful to many people.
637 questions
OpenID was previously the main login flow for Stack Exchange; it has since been deprecated.
636 questions
a flag that can be applied to answers (and sometimes questions) which lowers the barrier for editing and prevents any rep gain/loss from voting.
612 questions
designed to help new reviewers hone their moderation skills, while nudging more experienced users that don't seem to be paying close attention to what they're revi…
608 questions
for questions regarding off topic questions, including whether a question is on topic and what to do with off topic questions. DO NOT use this tag to post questions you know to be off-topi…
577 questions
for questions specific to upvotes, the community's way of telling peers that their content was clear and helpful. Up-votes on the meta sites may have different meanings.
575 questions
Questions about the meta site that every Stack Exchange site has (also called 'child metas').
for general questions about users and user accounts.
551 questions
Anything related to posts of low quality, such as flagging posts for "very low quality", or the low quality posts review task.
548 questions
3 4 5